Method for manufacturing externally pressurized bearing assemblies

Abstract

A novel means for manufacturing a precision linear or rotary motion system that is comprised of one or a set of precision machine bearing rails (i.e., long straight and parallel surfaces, or a single straight shaft), precision manufactured modular bearing pads, and a carriage or housing that surrounds the bearing pads when they are placed onto the rails and held in place by placing a vacuum on the port normally used to supply pressurized lubricant to the bearing rails, but leaves a gap between the rough surface of the housing or the carriage and the backsides of the bearing pads, into which gap a stable epoxy is injected to fill the gap between the backs of the bearing pads and the inner rough surface of the carriage. These goals are achieved first by designing the bearing rails or shaft to have the required straightness and parallelism tolerance, and the carriage or housing to have the required stiffness, such that when the bearing pads are epoxy-potted in-place and the external pressure source for the lubricant is turned on, the system expands enough to provide a sufficient and even fluid or gas film between the bearing pad surface and the rails or shaft as the carriage or housing moves through its complete range of motion with respect to the shaft. Alternatively, thin shim stock with holes in it (e.g., 10 micron thick) can be placed between one or more of the bearing pads and the rail prior to turning on the vacuum. After the epoxy is injected and cured, the shim stock is easily removed when the pressure is turned on.

What is claimed is: 
     
       1. A method for manufacturing a precision linear or rotary motion system using pressurized fluid bearings and comprised of one or a set of precision machine bearing rails and having a predetermined region where the pressurized fluid is normally applied to the bearing rails, precision manufactured modular bearing pads and a carriage/housing with rough inner surfaces that surround the bearing pads as placed on the rails, that comprises putting the bearing pads in place inner side down on the rails; applying vacuum only between pads and rails at said predetermined region to hold the bearing pads flat in their desired places while leaving a gap between rough surfaces of the carriage/housing and the outer sides of the bearing pads; injecting a stable epoxy to fill said gap between the outer sides of the bearing pads and the inner rough surfaces of the carriage to pot the bearing pads in precisely aligned place; and withdrawing the vacuum and applying the pressurized bearing fluid between the inner sides of the bearing pads and the rails to provide an operating fluid film therebetween. 
     
     
       2. A method as claimed in claim 1 and in which the bearing pads are fluid self-compensating and the fluid is water. 
     
     
       3. A method as claimed in claim 1 and in which the bearing pads comprise porous graphite and the fluid is air. 
     
     
       4. A method as claimed in claim 1 and in which the bearing pads use pockets and a fluid flow regulation device to regulate the flow into the pockets.